1. Field of the Invention
This invention relates to a V-type multicylinder internal combustion engine mounted on small cars such as motor cycle and motor tricycle and, more particularly, to that for which a crankshaft is arranged transversely of a car body, i.e. in the direction orthogonal to the longitudinal direction of the car body.
2. Description of the Prior Art
Conventional internal combustion engines of the mentioned type have such construction that a plurality of cylinder blocks are arranged in a V shape along the longitudinal direction of a car body, and pistons slidably fitted in cylinders formed in the cylinder blocks are rotatably coupled to a crank pin of a crankshaft through connecting rods. However, in the case where the connecting rods are coupled to the common crank pin at their large ends, the front and rear cylinder blocks must be arranged in dislocation from each other axially of the crankshaft at least by the axial length of the large end of each connecting rod.
Then, a crank and transmission case is formed uniformly on the lower ends of cylinder blocks, in which case are accommodated the crankshaft and a speed change gear coupled to the crankshaft by way of a primary reduction gear and a clutch.
Front and rear cylinder heads are fixed on the front and rear cylinder blocks, respectively, through gaskets. Front and rear cam shafts are mounted rotatably on the front and rear cylinder heads, and head covers are fixed thereon through packings. Front and rear timing chains are laid between front and rear driven sprockets fixed to the cam shafts and front and rear driving sprockets fixed to both ends of the crankshaft, respectively, so that the front and rear timing chains are disposed separately on both ends of the crankshaft.
The front cylinder block, front cylinder head, front gasket and front head cover are therefore different in structure from the rear cylinder block, rear cylinder head, rear gasket and rear head cover, respectively, therefore these parts cannot be used in common with each other, and the front and rear driving sprockets on both sides of the crankshaft must be wrought and assembled separately, for which exactly the same precision is hardly obtainable, thus involving a disorder, in most cases, in the operating timing for suction and exhaust valves of the front and rear cylinders actuated on rotations of the front and rear cam shafts.